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#36678
27.0.50; imenu not working in C++ (maybe because of namespace)
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Hello, Ergus.
On Wed, Jul 31, 2019 at 17:56:13 +0200, Ergus wrote:
> Hi Alan:
> Sorry for the long delay replying this.
No problem!
> I have been thinking on this for a while because this issue affects me
> constantly as I use most of the time C++ now.
I've actually spent some time on this. What I now have is the ability of
imenu to find functions, even when they are not at column zero, and to
record the enclosing namespace/class/etc. of these functions. On M-x
imenu <tab>, which lists all found functions (more or less), the
namespace/class bit only gets displayed as needed to distinguish from
other functions of the same name.
The above is a bit of an exaggeration: it is not yet clean or robust
code, and hasn't been tested much, but does sort of work on the files
I've tried it on.
What is still missing is a scanning of a function's parameters, needed to
distinguish, say, a constructor with two parameters from the same with
none. This is still looking a bit tricky.
> Maybe this is a stupid suggestion, but I was thinking that if the issue
> is performance (for ii) we could add a special function to implement the
> expensive part for the functional search in C and use the C regexps.
At the moment, the scanning of these C++ files is taking a small number
of seconds on my (pretty fast) Ryzen machine. This is slow for imenu.
I can't honestly see how we might use a C function to speed all this up.
Currently, my new code is just using (c-beginning-of-defun -1) to find
the next function, thus avoiding the need to write reams of syntactical
analysis code, but not being fast.
> Maybe it could be restrictive somehow, but if this solves a problem,
> could be good enough and important for C++-mode. Because namespace use
> is becoming more and more extended in C++ with the new standards. And
> the most common indentations are the
> Probably:
> 1) For example it could do a first filtration for the buffer in a C
> function using C regexp (with fake positives) and then filter again in
> the Lisp side?
> 2) Or, we could just iterate the file by lines in C and then modify the
> regex for the next line conditionally (which is cheaper than in
> Lisp). This could create a list in C that we can then use in the Lisp
> side more efficiently.
All this might be workable, I just don't know. But it would probably
make sense to write it in Lisp first, and only then optimise it with C if
it really is too slow.
> In case we figure out a nice method for that. Does it makes sense?
[ .... ]
--
Alan Mackenzie (Nuremberg, Germany).
This bug report was last modified 5 years and 316 days ago.
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